Adjustable means of limiting driving depth with attachable nosepiece



R. C. FALTER WITH ATTACHABLE NOSEPIECE Filed Jan. 24, 1968 INVENTORRONALD C. FLTER BY in@ /u. i@ #X07 ATTORNEYS sept. s, 1970 ADJUSTABLEMEANS 0F LIMITING DRIVING DEPTH NUnited States Patent O 3,527,273ADJUSTABLE MEANS 0F LIMITING DRIVING DEPTH WITH ATTACHABLE NOSEPIECERonald C. Falter, Columbia, S.C., assignor to Rockwell ManufacturingCompany, Pittsburgh, Pa., a corporation of PennsylvaniaContinuation-impart of application Ser. No. 585,824, Uct. 1l, 1966. Thisapplication Jan. 24, 1968, Ser. No. 709,168

Int. Cl. B25b 23/100 U.S. Cl. MAP-32 4 Claims ABSTRACT OF THE DISCLOSUREA tool including a detachable housing, an axially movable, rotatable,work-performing component disposed in the housing, a clutch located inthe housing which disengages to terminate rotation of thework-performing component when the work-performing component reaches apredetermined position longitudinally of the housing, a detachable stopmember adjustable axially of the housing for varying the distance thatthe end of the work performing, component protrudes from the housingwhen the clutch disengages, a keeper for retaining the stop member inthe position to which it is adjusted, and a removable nosepiece whichpermits the work-performing cornponent to 'be removed from the toolwithout disturbing the depth adjustment.

This application is a continuation-impart of application No. 585,824filed Oct. 1l, 1966 for Adjustable Means of Limiting Driving Depth WithAttachable Nosepiece (which is now abandoned).

This invention relates to tools and, more specifically, to tools forsetting a fastener or boring or tapping a hole at a specific distancerelative to a given work surface or the like. ln particular, then, thepresent invention relates to novel improved tools with an arrangementfor limiting the movement of the 'work performing tool element relativeto a given surface of a workpiece.

The principles of the present invention will be developed by relatingthem to drywall Screwdrivers for the sake of convenience. Theapplication of these principles to other types of tools will `be obviousto those skilled in the relevant arts from this description of anexemplary adaptation.

One important and primary object of the present invention is theprovision of tools with novel, improved, depth limiting devices.

In the depth limiting devices of the present invention by which thepresent and other important goals are achieved, a stop element threadedon the tool housing is employed to permit accurate adjustment of thedepth limit. A spring biased keeper having locking portions engageablewith cooperating portions on the threaded meinber is employed topositively lock the latter against rotational movement relative to thetool housing.

Co-operating with the depth limiting device just described in thepresent arrangement is a clutch interposed in the drive train betweenthe tool motor and the screwdriver bit or other work performingcomponent. In the case of a screwdriver type tool, for example, thisclutch automatically disengages when the bit has set the screw at aspecified depth determined by the stop element of the depth adjustingmechanism.

Tools employing a combination of depth adjusting mechanism andco-operating clutch have heretofore been proposed. Exemplary of but byno means the only such tool is the Milwaukee Electric Tool Co. CatalogNo. 6740-1 Drywall Screwdriver.

The novel tools of the present invention differ from those of the typedescribed in the preceding paragraph in one important respect. This isthat all of the components of the rotation effecting clutch mechanismare accessible merely 'by removing the housing on which the stop elementof the depth adjusting mechanism is threaded. In the previously proposedtools of the same general type, in contrast, the driving or both thedriving and driven clutch members are located in the main tool casing.

The advantage of applicants arrangement is than the clutch mechanism canbe serviced much easier than is possible in the previously proposedtools. Accordingly, maintenance costs are potentially lower in the caseof the present invention.

Another important advantage of applicants novel arrangement is that itpermits the reduction gears interposed between the tool motor and theclutch to be isolated in a sealed chamber in the main tool casing. Thisis advantageous since it facilitates lubrication of the reduction gearsand protection of the gears against dust and other foreign matter.

Still another advantage of applicants arrangement is that it facilitatesthe conversion of a drywall screwdriver to a regular drill and viceversa. For example, by merely replacing the detachable housing of thetype described above with one equipped with a conventional chuck and alink for connecting the chuck to the output shaft from the reductiongears, a drywall screwdriver can be quickly converted to a conventionaldrill.

Another feature of the present invention is that it utilizes in thedepth adjusting mechanism described above a nosepiece which can bereadily removed and which, when removed, permits the tool to be used toback out screws which have already been set.

`In the depth limiting devices of the present invention, by which theforegoing and other important goals are obtained, a stop elementthreaded on the tool housing is employed to permit accurate adjustmentof the depth limit. A spring biased keeper with locking portionsengageable with cooperating portions on the threaded member is employedto positively lock the threaded member against rotation on the toolhousing. As a result, lvibrational and other forces cannot alter thesetting of the stop element.

This arrangement has a decided advantage over drywall Screwdrivers andother tools equipped with different types of depth limiting devices.Specifically, in the case of a drywall screwdriver equipped with aconventional depth limiting device, the screw cannot be backed out withthe screwdriver unless the depth limiting component is iirst retracted.This is because the stop element prevents the screwdriver from turningthe screw once the latter has been set to the desired depth. In priordepth limiting devices the stop element cannot be retracted without thenreadjusting the device to its original setting to resume the driving ofscrews. This is decidedly disadvantageous since the time spent inreadjusting the stop element is completely non-productive.

In the depth limiting devices of the present invention, in contrast, thenosepiece of the stop element can be removed and replaced withoutaltering the depth adjustment when the circumstances dictate itsremoval, eliminating the time lost in readjusting the conventional depthlimiting device.

Tools with removable nosepieces have heretofore been proposed, a typicalexample being the Millers Falls Company No. 9637 Drywall Screwdriver.However, it has not been known that by employing them with depthlimiting mechanisms of the type contemplated by the present invention,the problem associated with the latter of backing out screws, etc.without disturbing the depth adjustment can be eliminated. Accordingly,the use of a removable nosepiece in the manner contemplated by applicantrepresents a significant advance in the art.

From the foregoing it will be apparent that other important but morespecific objects reside in the provision of tools in accord with thepreceding object:

(1) Which are significantly easier to service than heretofore knowntools of a similar type.

(2) Which are more flexible than heretofore known tools of a similartype in that they can be readily converted from use in one type ofoperation to use in another type of operation.

(3) Which facilitate the sealing of gear reduction drives and similardrive train components.

(4) Which in screw driving and similar applications permit screws andthe like to be backed out without disturbing the adjustment of the depthlimiting mechamsm.

Additional objects and advantages and other important novel features ofthe present invention will become apparent from the appended claims andas the ensuing detailed description and discussion proceeds inconjunction with the accompanying drawing, in which:

FIG. l is a partly sectioned side view of a drywall screwdriver equippedwith a depth limiting device having the advantages of and constructed inaccord with the principles of the present invention;

FIG. 2 is a section through the depth limiting device illustrated inFIG. l, taken substantially along line 2 2 of the latter figures;

FIG. 3 is a section through the depth limiting device of FIG. l, takensubstantially along line 3 3 of the latter gure;

FIG. 4 is a section through the depth limiting device of FIG. 1, takensubstantially along line 4 4 of the latter ligure;

FIG. 5 is a side view of the depth limiting device in one of thepositions to which it may be adjusted; and

FIG. 6 is a fragmentary side view of the depth limiting device inanother of the positions to which it may be adjusted.

Referring now to the drawing, FIG. 1 illustrates a drywall screwdriver10 equipped with a depth limiting device 12 constructed in accord withthe principles of the present invention.

In addition to the components just mentioned, screwdriver 10 includes acasing 14 housing an electric motor (not shown) connected to a gearreduction drive having a rotatably mounted output shaft 16. Theoperation of the screwdriver motor is controlled by an on-ofrr switch 18and a switch 20' for reversing the direction of motor rotation. A lockwith an actuator 22 is also preferably provided for locking motoractuating switch 18 in the on position.

The details of the components described 'briefly in the precedingparagraph are not part of the present invention. For this reason andbecause they may be of conventional construction, they will not bedescribed to an appreciably greater extent herein.

In the present invention, a clutch input member 24 having teeth 26formed on its forward face (see FIG. l) is fixed to gear reduction driveoutput shaft 16 for rotation therewith and prevented from moving axiallyof the shaft as by a retainer 27 (see FIG. 4). Axially aligned withclutch input member 24 is a clutch output member 28. The output memberhas teeth 30 on its rearmost face. These are engageable with the teeth26 on the clutch input member to provide a positive drive connectionbetween the two clutch members.

Clutch youtput member 28 is rotatably journalled in an elongatedcylindrical housing 32, which is threaded onto a mounting boss 34 at thefront end of tool casing 14. A shouldered spacer 36 adjacent boss 34provides a seal between tool casing 14 and housing 32. It also preventshousing 32 from being threaded on the boss so tightly as to damagecasing 14, which will normally be fabricated of a relatively softmaterial such as an aluminum alloy.

As shown in FIG. 1, clutch input member 24 is also housed in removablehousing 32 and is accordingly accessible when the latter is removed.This arrangement accordingly simplifies servicing of the tool and alsomakes it possible to seal the gear reduction drive terminating in outputshaft 16 within the main tool casing 14. As a result, the lubrication ofthe gear reduction drive and the sealing of its components against dustand other foreign matter is simplified.

Another advantage of the arrangement just described is that screwdriver10 can be readily converted to a conventional drill, for example, simplyby replacing housing 32 with one provided with a conventional chuck anda link for drive connecting the chuck to output shaft 16. Screwdriver 10can of course be similarly converted for use in other types ofoperations.

Referring still to FIG. 1, clutch output member 28 is free to moveaxially in an enlarged cavity 38 in housing 32 between positions inwhich it is respectively engaged with and disengaged from clutch inputmember 24. In the illustrated disengaged position, an external shoulder40 on the clutch member engages a co-operating internal shoulder 42 inhousing 32. In the engaged position, the teeth 30 of the clutch outputmember are engaged with the teeth 26 of clutch input member 24.

Clutch output member 28 is biased toward the illustrated disengagedposition by a coil spring 43, which surrounds gear reduction driveoutput shaft 16.1 As shown in FIG. l, the latter extends into a bore 44through clutch output member 28, and opposite ends of spring 43 pressagainst spring seats 46 and 48 formed on facing portions of the clutchoutput and input members.

Referring now to FIGS. 1 and 3, clutch output member 28 is provided, atits forward end, with a socket 50 in which screwdriver bit 52 isretained to drive connect it to clutch member 28. Socket S0 and the rearend of screwdriver bit 52 have matching polygonal congurations so thatthere is a positive drive connection between the clutch member and toolbit.

Screwdriver bit 52 is retained in socket 50 by a ball 54 seated in aconcave annular seat 56 adjacent the rear end of the screwdriver bit.Ball 54 extends through an opening 58 in the forward portion of theclutch output member and is pressed against tool bit seat 56 by a springmember 60 disposed in a recess 62 in the forward end of the clutchmember.

To drive a screw with screwdriver 10, the tip 64 of screwdriver bit 52is engaged with the grooves in the screw head. Forward pressure is thenexerted on tool casing 14 to move clutch input member 24 into drivingengagement with clutch output member 28. Switch 18 is then depressed toactuate the screwdriver motor which, through the gear reduction drive,clutch input member 24, and clutch output member 28 rotates screwdriverbit 52 to drive the screw.

In driving screws into gypsum board and other materials, it is generallynecessary to set the screw with its head flush or at a predetermineddistance below the surface of the work piece into which it is driven. Toaccomplish this, drywall screwdriver 10 is provided with a novel depthlimiting device 12 as mentioned above. Referring now specically to FIG.1, depth limiting device 12 includes two major components: a stopelement 66 (actually an assembly in the present invention as will becomeapparent later) and a keeper element 68.

As shown in FIGS. l and 5, stop element 66 is threaded onto the forwardend of housing 32. Rotation of element 66 on housing 32 accordinglymoves the stop element axially of the housing, varying the distancebetween lThe need for `a compression spring can be eliminated byproviding inclined surfaces on the clutch members so that relativerotation of the members will force them apart in the absence of anoperator-exerted force holding them in engagement.

the work contacting end 70 of the element and the end of screwdriver bittip 64, as may be seen by comparing FIGS. and 6. As will be describedlater, this is effective to vary the depth to which a screw will beseated by screwdriver 10.

Referring still to FIGS. 1 and 5, stop element 66 is positively lockedin the position to which it is adjusted by the keeper element `68mentioned previously. This element is a cylindrical sleeve mounted onthe forward end of housing 32 behind stop element 66. Keeper element 68is free to move axially on the housing, but is prevented from rotatingrelative to the housing as by a setscrew 72 which extends through thekeeper element into an elongated groove 74 cut in and extending axiallyof housing 32.

As is best shown in FIG. 5, the forward end of keeper element 68 isprovided with projections or teeth 76, which fit into co-operating andsimilarly configured notches or recesses 78 formed in the rear end ofstop element 66. There are two teeth 180 apart and four recesses 90apart in the illustrated embodiment of the present invention. A largernumber of teeth or recesses or both may, of course, be employed, ifdesired.

With projections 76 engaged in recesses 78, keeper element 68 and stopelement 66 must necessarily rotate as a unit. However, since rotation ofthe keeper element is prevented by setscrew 72, such engagement locksstop element 66 against rotation relative to housing 32, therebypositively retaining it in the position to which it is adjusted.

The arrangement just described positively prevents stop member 66 frombeing shifted out of adjustment by vibration or other external forces ascommonly occurs in depth limiting devices in which friction is reliedupon to lock the stop member in place.

Referring now to FIG. l, keeper element 68 is biased toward stop element66 by a compression spring 80 housed between co-operating internal andexternal recesses 82 and 84 in keeper element 68 and housing 32,respectively. As shown in FIG. 1, the ends of recesses 82 and 84 arespring seats against which the opposite ends of spring 80 press to biaskeeper element 68 toward stop element 66. This arrangement is highlyeffective in maintaining keeper element 68 in locking arrangement withstop element 66.

At the same time, it permits the setting of the stop element to beeasily and quickly adjusted. To accomplish this it is necessary only toretract the keeper element until teeth 76 clear recesses 78, rotate thestop element to the new setting, and release the keeper element (whichwill then move forward under the iniiuence of spring 80 into engagementwith the stop element). Stop element 66 is then rotated a few degrees(if necessary) until teeth 76 drop into recesses 78 under the influenceof spring 80.

The slight rotation which may be necessary to engage teeth 76 inrecesses 78 will not effect the setting to any appreciable extent. Thisis particularly true as the number of locking teeth is increased.

Referring again to FIG. 1, as screwdriver bit 52 is rotated in themanner described above, sinking the screw driven by the bit further intothe work piece, the work contacting end 70 of stop element 66 approachesand finally engages the surface of the work piece. With stop element 66adjusted as shown in FIG. 5, for example, screwdriver bit 52 willcontinue to rotate at this point, setting the screw deeper into the workpiece. However, with the stop element abutted against the work piece,the tool cannot be moved forwardly to maintain clutch input member 24 inengagement with clutch output element 28. Accordingly, as the screwdriven by bit 52 continues to sink deeper into the work piece,compression spring 43 will move the teeth 30 on the clutch output member28 out of engagement with the teeth 26 on clutch input element 24. Atthis point, which will occur when the screw has been driven to thedesired depth, the screwdriver bit will cease to rotate. As will beapparent from the description of screwdriver 10 set forth above and acomparison of FIGS. 5 and 6, the distance between the work engaging end70 of stop element 66 (and accordingly the work piece surface) andscrewdriver bit 52 at which separation of the clutch members occurs canbe readily varied by adjusting the stop element along housing 32 in themanner described previously.

At times, it may be necessary to remove a screw which has been set. Whenemploying a tool equipped with a conventional depth limiting device,screw removal cannot be accomplished without altering the adjustment ofthe depth limiting device, which is decidedly disadvantageous.Specifically, it will be remembered that clutch members 24 and 28separate to stop rotation of bit 52 when the screw driven by the bitreaches the desired depth. A similar declutching occurs in a toolequipped with a conventional depth limiting device. Accordingly, topermit re-engagement of the clutch members in a tool equipped with theconventional device, the work contacting stop element must be retractedso that the tool can be moved sufliciently far toward the work tore-engage the clutch members, which alters the depth adjustment of thestop element.

`In the present invention, the necessity of readjusting stop element 66to effect screw removal is overcome by the two-piece construction ofthis element, which includes an adjusting member 86 and a Workcontacting nosepiece S8. As shown in FIG. 1, adjusting member 86 is ofcylindrical configuration and is provided with internal threads 90engaging the threads on housing 32. The recesses 78 into which theprojections 76 of locking element 68 extend are also formed in thismember.

Nosepiece 88 is an elongated cylindrical member seated in an annularrecess 92 at the forward end of adjusting member 86. The nosepiece isfrictionally retained in place by an O-ring 94.

To remove a screw that has been set, it is only necessary to removenosepiece 88, which does not require any retraction or other shifting ofstop element adjusting member 86. Removal of the nosepiece permits tool10 to be moved sufficiently far forward to engage clutch elements 24 and28. Switch 20 may then be moved to its reverse position and switch 18depressed to actuate the tool motor and back out the screw. Followingthis, nosepiece 88 can be quickly reseated on adjusting member 86 andthe setting of screws resumed.

Another advantage of the novel two-piece stop element just discussed isthat interchangeable nosepieces may be seated on the adjusting member.This is advantageous in that it permits a nosepiece to be selected whichwill not mar or otherwise damage the particular type of material withwhich it is in contact, for example. The removable nosepiece also makesit possible to use different types of screwdriver bits or other workcontacting elements and substantially facilitates the replacement ofthese elements.

As will be apparent from the foregoing description and as mentionedabove, the principles of the present invention may be readily adapted totools other than drywall Screwdrivers. By slight modifications ofvarious components and substitutition of a different type of rotatableworking element for the screwdriver bit employed in a drywallscrewdriver, the invention described above can be readily adapted todrilling and tapping tools, stud setters, nut runners, and other toolswhere movement of the rotating work producing component to a particulardepth is desired. Accordingly, such modifications of the presentinvention are fully intended to be covered in the appended claims to theextent that they are not expressly excluded therefrom.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiment is therefore to be considered in all respects as illustrativeand not restrictive, the scope of the invention being indicated by theappended claims rather than by the foregoing description, and allchanges which come within the meaning and range of equivalency of theclaims are therefore intended to be embraced therein.

What is claimed and desired to be secured by Letters Patent is:

1. A tool comprising a casing; a motor in said casing; a housing iixedto said casing; a work-performing cornponent rotatable in and movableaxially relative to said housing; clutch input and output membersrotatably mounted in said housing, said input member beingdriveconnected to said motor and being axially fixed relative to thehousing, said output member being axially movable in the housing; meansby which the rotatable tool component can be attached to said outputmember for rotation therewith; and means for terminating rotation ofsaid component when it reaches a predetermined position longitudinallyof said housing comprising means capable of biasing said output elementout of driving engagement with said input element; a stop having an endadapted to engage a work piece surface and including a first memberadjustable axially of said housing to vary the distance an end of saidrotatable component is from the work piece engaging end of said stopwhen rotation of said component is terminated and a second member onwhich said work piece engaging end is formed having a portionsurrounding said rst member; a keeper engageable with said iirst stopmember to retain said stop in the position to which it is adjusted; anda friction member between said -irst stop member and said second stopmember for retaining said second member on said first member, wherebysaid second stop member may be readily detached from said rst stopmember to thereafter permit said housing to be moved toward said workpiece to 1re-engage said clutch input and output members and effectfurther rota- 3 tion of said work-performing component.

2. The tool of claim 1, together with a gear reduction drive operativelyconnected to said motor and disposed in the casing in which said motoris mounted, said gear reduction drive including a rotatable drive shafthaving the clutch input member iixed thereto extending into a blindaperture in the clutch output member, said biasing means being acompression spring in said aperture between the end of the drive shaftand the blind end of the aperture.

3. The tool of claim 1, wherein said keeper is movable axially of butnon-rotatable relative to said detachable housing, said stop is threadedon said housing, and said stop and keeper have cooperating abutmentelements engageable to positively prevent said stop from rotatingrelative to said keeper.

4. The tool of claim 3, together with means biasing the keeper intoengagement with the stop including a spring surrounding said detachablehousing and interposed between the housing and keeper, opposite ends ofsaid spring engaging abutments on said housing and said keeper,respectively, whereby said spring biases said keeper relative to saidhousing and into engagement with the stop. References Cited UNITEDSTATES PATENTS 2,242,510 5/ 1941 Cogsdill 77-55 v2,402,353 A6/ 1946Trautmann 77-55 .2,670,644 3/,1954 Du Sell 144-32 2,790,471 4/ 1957Graybill 144-32 2,796,161 6/ 1957 Graybill 144-32 2,940,488 6/1960 Riley144--32 GERALD A. DOST, Primary Examiner Us. C1. xn.

